One important component of electrical vehicles is the secondary battery system, which provides power to the vehicle and determines vehicle performance. In many applications, this battery is a lithium secondary battery, for example, a solid state lithium secondary battery. Secondary batteries, as opposed to primary batteries, are rechargeable.
Lithium ion and lithium metal batteries are useful in automotive applications because of their high specific energy and energy density, long cycle life, high round trip efficiency, low self-discharge, and long shelf life. However, some of these batteries exhibit poor low temperature performance, for example, low power output despite having a high energy density. For example, it has been reported that lithium ion cells can lose up to 88% of their room temperature capacity at below −40° C. (See, for example, E. J. Plichta and W. K. Behl, in Proceedings of the 38th Power Sources Conference, Cherry Hill, N.J., p. 444 (1998)).
Furthermore, some next-generation battery technologies and designs are moving in the direction of improving energy density, but may have lower power availability at low or moderate temperatures. Such next-generation batteries may need to be warmed up to 40, 60, or perhaps even 80 degrees Celsius to provide full power.
One strategy to increase low temperature battery performance includes pre-warming of the battery system before use of the battery. As the battery temperature increases, the battery performance increases accordingly and often exponentially so. Pre-warming the battery increases the power available when the vehicle/battery is used.